1. Field of the Invention
The present invention relates generally to a control device having an output pin expansion function and an output pin expansion method, and more particularly, to a control device that uses a shift register unit for achieving an output pin expansion function and an output expansion method.
2. Description of Related Art
Generally, various functions of electronic devices, such as computer systems, server systems and network devices, are indicated by LEDs that are driven by signals output from general purpose I/O (GPIO) pins of central processing units of the electronic devices. For example, a wireless network router with a wireless internet access function has a plurality of LEDs for indicating the operating state of the wireless internet access, such as indications for sysbooting, sysready, Wlanddisconnect, WlanWpsScan, Wlan11aMode, Wlan11gMode, WlanInactivity, WlanRateLow, WlanRateHigh, WlanRateMid, EthernetActivity and so on. Accordingly, a great number of LEDs need to be disposed in a wireless network router for such indications. However, a wireless network router typically lacks enough GPIO pins for driving so many LEDs.
Consequently, many logic gates and complex circuits are added to printed circuit boards to expand the number of GPIO pins. However, this consumes a lot of space on the printed circuit boards and cannot be applied to products with limited space.
Therefore, there is a need to provide a control device having an output pin expansion function and an output pin expansion method so as to overcome the above drawbacks.